Patients with chronic diseases are often prescribed drugs which may be taken hourly, daily, weekly, etc. and therefore, a pen type drug delivery device was developed to provide the patient, who does not have formal medical training, to perform self-injection periodically.
Currently, there are two types of pen type drug delivery devices, namely, disposable (i.e., non-resettable) and reusable (i.e., resettable). These types of pen delivery devices are generally comprised of three primary elements: (i) a cartridge section that includes a cartridge contained within a holder; (ii) a needle assembly connected to one end of the cartridge section; and (iii) a dosing section connected to the other end of the cartridge section.
The cartridge includes a reservoir that is filled with a drug (e.g., insulin), a movable rubber type bung located at one end of the cartridge reservoir, and a top having a pierceable rubber seal located at the other end. While the cartridge housing may be typically made of plastic, cartridge reservoirs have historically been made of glass.
The dosing section is the portion of the pen device that is used to set a dose. During an injection, a screw spindle contained within the dosing section presses against the bung of the cartridge. This force causes the drug contained within the cartridge to be injected through an attached needle assembly.
Disposable pen delivery devices do not have removable pre-filled cartridges. Rather, the pre-filled cartridges may not be removed and replaced from these devices without destroying the device itself. Therefore, these disposable devices do not need to have a resettable dose setting mechanism.
In contrast to disposable pen delivery devices, typical reusable pen delivery devices feature two main reusable components, namely, a cartridge holder and a dose setting mechanism.
After a cartridge is inserted into the cartridge holder, the cartridge holder is attached to the dose setting mechanism. The user may use the dose setting mechanism to select a dose. After the drug in the cartridge has been exhausted, the user may detach the cartridge housing from the dose setting mechanism. The user may then remove the empty cartridge from the cartridge holder and replace the empty cartridge with a new cartridge.
In order to reset the reusable pen delivery device, aside from replacing the empty cartridge with a new cartridge, the dose setting mechanism must be reset to an initial position. For example, in certain typical reusable pen delivery devices, in order to reset the dose setting mechanism, the screw spindle that advances in a distal direction during dose injection must be retracted back into the dose setting mechanism.
Known reset mechanisms require a user to push back (i.e., retract) the screw spindle or some other portion of the dose setting mechanism back into the mechanism.
Known reusable pen delivery devices have certain perceived disadvantages. One perceived disadvantage is that the user has to disassemble the device to either remove an empty cartridge or reset the device. Another perceived disadvantage is that such devices have an increased number of parts and therefore such devices are typically complicated from a manufacturing and from an assembly standpoint.
For example, known reusable pen type devices are not intuitive as to how a user may replace an empty cartridge and reset the device. In addition, because such reusable devices use a large number of components, such reusable devices tend to be large and bulky, and therefore not easy to carry around or transport.